Mobile station apparatus and method for transmitting signals in wireless communication system

ABSTRACT

A method for transmitting signal, at a mobile station, in a wireless communication system is provided. Inter-cell interference level control parameter information may be different for each frequency partition due to use of an FFR scheme. This method is advantageous in that, when uplink transmission is performed, system throughput and cell edge-user throughput are improved and inter-cell interference level control is efficiently performed, thereby improving a Signal to Interference plus Noise Ratio (SINR) at the receiving end.

TECHNICAL FIELD

The present invention relates to a wireless communication system, andmore particularly, to an MS apparatus and method for transmittingsignals using an FFR scheme.

BACKGROUND ART

In a Orthogonal Frequency Division Multiple Access (OFDMA) system ofmulti-carrier scheme, resources are allocated in units of subchannels,each including subcarriers. A plurality of users separately share allsubcarriers, so multi-user diversity gain is obtained in frequencyregion. In an OFDMA broadband mobile Internet access system such asWiBro, all cells reuse the same frequency and an Adaptive Modulation &Coding (AMC) scheme is applied according to received signal strength andinterference between neighbor cells due to reuse of the same frequency,thereby maximizing throughput.

However, in such a system having a Frequency reuse Factor (FRF) of 1,inter-cell interference is severe and throughput reduction is inevitableat edges (i.e., boundaries) of cells or sectors. This may cause serviceoutage. In a method for improving performance at cell edges when afrequency reuse factor of 1 is used, all subcarriers are orthogonallydivided into a number of frequency partitions and the frequencypartitions are appropriately arranged in cells such that a specificfrequency partition is not used or is used at low power in each cell,thereby reducing interference of the same channel between neighborcells. This method is referred to as a Fractional Frequency Reuse (FFR)scheme.

In order to apply FFR to an actual system, a band to be used in eachcell may be determined based on frequency partitions arranged in thecell according to location information of each Mobile Station (MS). Inactual situations, a signal to interference ratio may be dynamicallyreflected in determining which frequency partitions are to be used foreach cell among a band allocated to the cell since the signal tointerference ratio constantly varies in the same band due to movement ofthe MS, fading, etc.

In order to dynamically use resources taking into consideration thesignal to interference ratio or the like when partial frequencypartitions have been allocated to each cell as described above, it isnecessary to take into consideration fairness between users in additionto the given Frequency Reuse Factor (FRF).

When all subcarriers are orthogonally divided into a number of frequencypartitions in the OFDMA system as described above, various types of FFRschemes may be taken into consideration to allow cells to share thesefrequency partitions. The following is a description of the concept andcharacteristics of such FFR schemes.

As the FRF approaches 1, inter-cell interference due to use of the samechannel at cell edges may increase, thereby reducing communicationperformance, although the size of a band that is available in the cellincreases. On the other hand, as the FRF increases, the size of theavailable band decreases, thereby reducing band efficiency, althoughinter-cell interference due to use of the same channel decreases.

FIG. 1 illustrates an example FFR scheme.

Referring to FIG. 1, FFR is a method for increasing cell capacity anduser Quality of Service (QoS). In the FFR scheme, services are providedto users located near a Base Station (BS) using a frequency reuse factor(FRF) of 1 (i.e., using all subcarriers) to maximize total cell capacitysince the level of inter-cell interference will be relatively low forusers located near the BS from the viewpoint of the entire cell. In thecase where the FRF 1 is used, a FRF of 3 is used for cell-edge usersexpected to undergo a high inter-cell interference level (i.e., not allsubcarriers are used but instead part of the bands of FRF 3 is used foreach sector), thereby reducing inter-cell interference to provide highquality services.

FFR is classified into hard FFR in which frequency bands used bycell-edge users of other cells are not used and soft FFR in which suchfrequency bands are also used with restriction of power and specificconditions. The soft FFR scheme is a general concept including hard FFR.In the soft FFR scheme, neighbor cells set different transmission powerlevels for each frequency partition, thereby increasing overall cellcapacity. Here, the soft FFR scheme becomes a hard FFR scheme iftransmission power is set to 0.

FIG. 2 illustrates example hard and soft FFR schemes.

Referring to FIG. 2, in the case of the hard FFR scheme, only specificfrequency bands are used among frequency bands of FFR 1/3 in each cell.On the other hand, it can be seen that, in the case of the soft FFRscheme, all frequency bands of FFR 1/3 are at different power levels ineach cell. For example, the power level of the same frequency band ofFFR 1/3 may be different for each cell. In addition, each cell may havedifferent power levels for the frequency bands of FFR 1/3.

When the FFR scheme is applied, each frequency band generally has adifferent power level as shown in FIG. 2. The present invention suggestshow to set a power level for each FFR group or each frequency partitionand how to perform signaling in downlink and uplink.

DISCLOSURE Technical Problem

An object of the present invention is to provide a method fortransmitting signals in a wireless communication system.

Another object of the present invention is to provide an MS apparatusfor transmitting signals in a wireless communication system.

Objects of the present invention are not limited to those describedabove and other objects will be clearly understood by those skilled inthe art from the following description.

Technical Solution

A method for transmitting, at a mobile station, signals in a wirelesscommunication system to achieve the objects of the present inventionincludes receiving information a specific frequency partition allocatedto the mobile station according to a fractional frequency reuse scheme,receiving parameter information for controlling an inter-cellinterference level for each frequency partition from a base station,determining a transmission power level for the allocated specificfrequency partition using the received information, and transmitting asignal to the base station at the determined transmission power level.

The method may further include receiving, from the base station, atleast one of a minimum required Signal to Interference plus Noise Ratio(SINR), a factor value according to the number of receive antennas ofthe base station, and a value indicating a MAC power control mode.

The inter-cell interference control parameter includes defaultinter-cell interference control parameter information representing adefault value of each frequency partition and relative adjustmentinter-cell control parameter information representing a relativedifference value from the default cell interference control parametervalue of a specific frequency partition.

A frequency partition which uses the default inter-cell interferencecontrol parameter alone may be determined according to a number ofpredefined frequency partitions.

When the number of predefined frequency partitions is 1, the frequencypartition which uses the default inter-cell interference controlparameter alone may correspond to a frequency partition of a frequencyreuse factor of 1.

When the number of predefined frequency partitions is 3, the frequencypartition which uses the default inter-cell interference controlparameter alone may correspond to a specific frequency partition amongfrequency partitions of the frequency reuse factor of 3.

On the other hand, a specific frequency partition among frequencypartitions of a frequency reuse factor of 3 may be different for eachcell.

The default inter-cell interference control parameter value is equal forall frequency partitions or for a specific frequency partition groupamong the all frequency partitions or may be different for eachfrequency partition.

The default inter-cell interference control parameter value may besignaled in 4 bits from the base station.

The base station may notify the mobile station of the specific frequencypartition among the frequency partitions of a frequency reuse factor of3 is notified through broadcast signaling, or individual signaling ofeach mobile station.

The specific frequency partition among the frequency partitions of afrequency reuse factor of 3 may be determined as a cell Identifier (ID)function.

The relative adjustment inter-cell interference control parameter valuemay be used for a specific frequency partition among frequencypartitions of a frequency reuse factor of 3.

The relative adjustment inter-cell interference control parameter valuemay be signaled in 2 or 3 bits from the base station.

The step of determining the transmission power level may includedetermining transmission power additionally taking into consideration adownlink signal to interference plus noise power ratio (SINR) measuredat the mobile station.

The determined transmission power level may be a transmission powerlevel determined for each stream and for each subcarrier.

The inter-cell interference control parameter may be determined throughcoordination between the base stations. The inter-cell interferencecontrol parameter may also be signaled to the mobile station through acontrol channel or message, wherein the control channel may be one of asuperframe header, an uplink Advanced-MAP Information Element (A-MAPIE), and Additional Broadcast Information (ABI).

Advantageous Effects

According to the present invention, when uplink transmission isperformed, it is possible to improve system throughput and celledge-user throughput and to efficiently perform inter-cell interferencelevel control.

Advantages of the present invention are not limited to those describedabove and other advantages will be clearly understood by those skilledin the art from the following description.

DESCRIPTION OF DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention, illustrate embodiments of the inventionand together with the description serve to explain the principle of theinvention.

In the drawings:

FIG. 1 illustrates an example FFR scheme.

FIG. 2 illustrates example hard and soft FFR schemes.

FIG. 3 illustrates an example FFR scheme.

FIG. 4 illustrates an example wherein a different SINR_target value isapplied in each frequency partition when the FFR scheme is applied.

FIG. 5 illustrates the operation of a soft FFR scheme in downlink.

FIG. 6 illustrates an example operation scenario of a base station and amobile station when a soft FFR scheme is applied in uplink.

FIG. 7 illustrates an example operation scenario of a base station and amobile station when a soft FFR scheme is applied in uplink.

FIG. 8 illustrates duality of a downlink transmission power level and anuplink target IoT level.

FIG. 9 illustrates an example wherein a different transmission powervalue is used for each frequency partition in the case where an uplinkFFR scheme is applied.

FIG. 10 illustrates an example wherein a sounding channel configurationis transmitted in one OFDM symbol at intervals of a predetermined frameperiod.

FIG. 11 is a block diagram illustrating a configuration of a preferredembodiment of a mobile station that can transmit signals according tothe present invention.

MODE FOR INVENTION

Reference will now be made in detail to the preferred embodiments of thepresent invention with reference to the accompanying drawings. Thedetailed description, which will be given below with reference to theaccompanying drawings, is intended to explain exemplary embodiments ofthe present invention, rather than to show the only embodiments that canbe implemented according to the invention. The following detaileddescription includes specific details in order to provide a thoroughunderstanding of the present invention. However, it will be apparent tothose skilled in the art that the present invention may be practicedwithout such specific details. For example, although the followingdescription will be given with reference to specific terms, the presentinvention is not necessarily limited to the specific terms and otherterms may also be used to indicate the same meanings. The same referencenumbers will be used throughout this specification to refer to the sameor like parts.

The expression “a portion includes a specific component” used throughoutthis specification indicates that the portion may also include othercomponents, rather than includes the specific component alone, unlessexplicitly stated otherwise.

Technologies described below can be used in a variety of communicationsystems, which can provide a variety of communication services such asvoice and packet data services. Communication system technologies can beused in downlink or uplink. The term “Base Station (BS)” may be replacedwith another term such as “fixed station”, “Node B”, “eNode B (eNB)”,“access point”, or “ABS”. The term “Mobile Station (MS)” may also bereplaced with another term such as “User Equipment (UE)”, “SubscriberStation (SS)”, “Mobile Subscriber Station (MSS)”, “AMS”, or “mobileterminal”.

The term “transmitting end” refers to a node that transmits data oraudio services and “receiving end” refers to a node that receives dataor audio services. Thus, in uplink, the MS may be a transmitting end andthe BS may be a receiving end. Similarly, the MS may be a receiving endand the BS may be a transmitting end in downlink.

A Personal Digital Assistant (PDA), a cellular phone, a PersonalCommunication Service (PCS) phone, a Global System for Mobile (GSM)phone, a Wideband CDMA (WCDMA) phone, or a Mobile Broadband System (MBS)phone may be used as the MS in the present invention.

The embodiments of the present invention can be supported by standarddocuments of at least one of the Institute of Electrical and ElectronicsEngineers (IEEE) 802 system, the 3GPP system, the 3rd GenerationPartnership Project Long Term Evolution (3GPP LTE) system, and the 3GPP2system which are wireless access systems. That is, steps or portionsthat are not described in the embodiments of the present invention forthe sake of clearly describing the spirit of the present invention canbe supported by the standard documents. For all terms used in thisdisclosure, reference can be made to the standard documents. Especially,the embodiments of the present invention can be supported byP802.16-2004, P802.16e-2005, P802.16Rev2, and P802.16m AWD or P802.16mdraft, which are standard documents of the IEEE 802.16 system.

Specific terms used in the following description are provided for betterunderstanding of the present invention and can be replaced with otherterms without departing from the spirit of the present invention.

The term “Base Station (BS)” used in the present invention conceptuallyincludes “cell” or “sector”, and can also be referred to as a cell orsector.

The present invention suggests how to set a power level for each FFRgroup or each frequency partition and how to perform signaling indownlink and uplink.

In addition, this specification describes a power control method forimproving performance of cell-edge user and performance of cell orsector system using a Fractional Frequency Reuse (FFR) scheme in uplink.An object of this power control method is to reduce interference and toachieve minimum cell-edge user performance. Another object of this powercontrol method is to improve performance in multi-user MIMO environmentswhile maintaining the same level of interference as in the single-userscheme. One main feature of this power control method is to minimizecontrol signaling in order to reduce overhead while achieving the sameperformance.

A system that uses the FFR scheme can use at least two frequencypartitions. When two or more frequency partitions are present, thefrequency partitions may undergo different communication environmentssuch as different channel characteristics, different interferencecharacteristics. This can be used for specific purposes. That is, when aMobile Station (MS) is in a bad channel condition, the MS can achieve animprovement in performance by using resources of frequency and timeregions in which a relatively low level of interference is measured.

FIG. 3 illustrates an example FFR scheme.

Referring to FIG. 3, four frequency partitions may be present andrelatively large power may be used in a specific one of the three FFR1/3 regions if the soft FFR scheme is used. It is preferable that theFFR 1/3 region be used for a specific MS which is in a bad channelcondition. It is necessary to take into consideration the amount ofinterference caused to other cells or sectors when performing power anduser allocation to the remaining two FFR 1/3 regions. This is becausethe benefits of the FFR scheme may not be achieved in the case where theresource allocation of the regions is not appropriate. In the presentinvention, it is possible to apply an algorithm suitable for eachfrequency partition in order to support a system, to which the FFRscheme is applied, to efficiently support such allocation. Thisalgorithm may operate based on an open-loop power control scheme.

Since propagation loss, interference, noise, and the like may operate asfactors reducing signal quality, to obtain signal quality required forthe receiving end, it is necessary to appropriately control transmissionpower so as to overcome such signal quality reduction factors.

Power control generally satisfies the signal quality required for thereceiving end by compensating for pathloss (or propagation loss),interference, and noise between the BS and the MS. Accordingly,transmission power may be determined taking into consideration a targetSignal to Interference plus Noise Ratio (SINR), noise (N), interference(I), and pathloss (PL) or may be determined taking into consideration atarget Carrier to Interference plus Noise Ratio (CINR), noise (N),interference (I), and pathloss (PL) as expressed in the followingMathematical Expression 1.

P _(tx) =f(SINR_(target) , N, I, PL) or f(CINR_(target) , N, I, PL)  [Mathematical Expression 1]

Mobile communication system may have pathloss according to distancesince electromagnetic waves are used as a transmission means. Suchpathloss may be caused by attenuation that electromagnetic or radiowaves undergo until arriving at a receive antenna after beingtransmitted from a transmit antenna, and may also be caused by changesin the distance between the transmitting and receiving ends due to themovement of the moving body or ambient environments.

Uplink power control in the IEEE 802.16e system is briefly described asfollows. In the IEEE 802.16e system, system performance can be improvedby performing power control taking into consideration not only the SINRor CINR, pathloss, interference, and noise but also offsets due to theBS and the MS (Δoffset_MS and Δoffset_BS) according to systemcharacteristics. This can be represented by the following MathematicalExpression 2.

P _(tx)=SINR+(I+N)+PL+Δ _(offset) _(—) _(MS)+Δ_(offset) _(—)_(BS)[dBm]  [Mathematical Expression 2]

Since interference due to neighbor cell is factor deteriorating systemperformance, it is necessary to control transmission power so as toovercome interference through power control in wireless communicationsystems. Transmission power is generally proportional to interferencepower. That is, increasing the transmission power to overcomeinterference causes an increase of interference caused to neighborcells, which then may cause the serving cell to receive strongerinterference from the neighbor cells. Accordingly, there is a need toprovide a power control method which appropriately controls interferencecaused to neighbor cells while ensuring signal quality required for thereceiving end.

Fractional power control compensates only for part of pathloss using apower control method for suppressing inter-cell interference (ICI). Thatis, if transmission power is reduced by compensating only for part ofpathloss, it is possible to reduce interference caused to neighborcells, resulting in a reduction of interference received from neighborcells. Such power control may be represented by the followingMathematical Expression 3.

P _(tx)=SINR +(I+N)+α·PL[dBm], 0<α≦1   [Mathematical Expression 3]

Here, α is a factor to compensate for part of pathloss.

The following is a description of a power control method to achieve atarget interference level.

A target interference level may be used as a method for minimizinginterference caused to neighbor cells while satisfying signal qualityrequired for the receiving end. The target interference level is a levelof interference to satisfy required signal quality at a receiving endand may be expressed using a variety of terms including inter-cellinterference terms (or elements) such as IoT, SINR, and CINR.

In the case inter-cell interference level in a cell or sector is greaterthan a level of required signal quality, the receiving end may request aneighbor cell or sector to restrict inter-cell interference and thisrequest may be signaled through a backbone link. Power control may beperformed through inter-cell coordination between BSs rather thanthrough an individual request.

A BS of a cell or sector has received a request to perform power controlfor limiting or reducing inter-cell interference or a BS performsinter-cell coordination with other BSs, the BS may control transmissionpower of the transmitting end as expressed by the following MathematicalExpressions in order to reduce inter-cell interference caused toneighbor cells or sectors.

P _(tx)=(1−α)P _(IoT) _(target) ÷αP _(intra) _(—) _(tx)

where, 0≦α≦1

if

α=1, IoT_(tar)≧IoT_(e)

α=0, IoT_(tar)<IoT_(e)   [Mathematical Expression 4]

P _(tx) =αP _(IoT) _(target) +(1−α)P _(intra) _(—) _(tx)

where, 0≦α≦1

if

α=1, IoT_(tar)<IoT_(e)

α=0, IoT_(tar)≧IoT_(e)   [Mathematical Expression 5]

Here, IoT_(tar) denotes a target level of inter-cell interferencerequired from a neighbor cell or sector, P_(intra) _(—) _(tx) denotestransmission power when inter-cell interference is not taken intoconsideration, IoT_(e) denotes an estimated level of interference causedto a neighbor cell or sector, and P_(IoT) _(target) denotes atransmission power level for satisfying IoT_(tar).

Here, ‘N’ may be omitted in the case where IoT_(term) does not includenoise unlike its original definition. P_(intra) _(—) _(tx) may berepresented as P_(intra) _(—) _(tx)=SINR_(tar)·PL_(s)·(I+N) and may alsobe represented as P_(intra) _(—)_(tx)=SINR_(tar)·PL_(s)·(I+N)·Δ_(offset) _(—) _(MS)·Δ_(offset) _(—)_(BS) taking into consideration BS offset and MS offset. The inter-cellinterference power I_(inter) is received as

${I_{inter} = \frac{P_{tx\_ intra}}{{PL}_{t}}},$

and IoT_(e) is received as

${IoT}_{e} = {{\frac{I_{inter} + N}{N} \approx \frac{I_{inter}}{N}} = {\frac{P_{tx\_ intra}}{P_{t}} \cdot {\frac{1}{N}.}}}$

If N>>1,

${IoT}_{tar} = {\frac{P_{{IoT}_{target}}}{{PL}_{t}} \cdot \frac{1}{N}}$

so that P_(IoT) _(target) =IoT_(tar)·PL_(s)·N.

In the case of Open Loop Power Control (OLPC) among power controlmethods for controlling inter-cell interference in which power controlis performed by the MS, the BS may transmit, to the MS, an interferencelevel (IoT_(tar)) for controlling inter-cell interference such as atarget IoT received from a neighbor cell or sector (or a target IoTdetermined through coordination between BSs or a target IoT randomlydetermined between BSs).

In the case where a system bandwidth is divided into multiple frequencypartitions as in the IEEE 802.16m system, a different interference levelmay be transmitted for each frequency partition or to each MS.

The interference level (target IoT, i.e., IoT_(tar)) for each frequencypartition may be determined as in the following Mathematical Expression6 or 7.

IoT_(tar)=ω·IoT_(default)[dB]  [Mathematical Expression 6]

IoT_(tar)=ω±IoT_(default)[dB]  [Mathematical Expression 7]

In Mathematical Expression 6 or 7, ω denotes a weight factor for settinga target IoT and can be obtained using the following equation. Thefollowing is a description of various methods for setting the targetIoT. In a first method, the target IoT can be represented by thefollowing Mathematical Expression 8.

IoT_(tar)=(1−γ)IoT_(min)+γIoT_(default)   [Mathematical Expression 8]

Here, a list that is signaled by the BS may include a minimum target IoT(IoT_(min)), a default target IoT (IoT_(default)) and an IoT adjustmentvalue γ (0≦γ≦1).

For example, when the number of frequency partitions is 4,IoT_(default)=7 dB, and IoT_(min)=4 dB, it may be possible thatIoT_(target) _(—) _(FP0)=4 dB, IoT_(target) _(—) _(FP1)=5 dB,IoT_(target) _(—) _(FP2=)6 dB, and IoT_(target) _(—) _(FP3)=7 dB, andγ_(FP0)=0, γ_(FP1)=1/3, γ_(FP2)=2/3, and γ_(FP3)=1.

Here, the default target IoT is a reference value of the target IoT setfor the each partitions in the case 20’ where multiple frequencypartitions are present and may be the average of IoT values in allsystem bandwidth, the average of the target IoT values of the eachfrequency partition, or the like.

Here, the default target IoT value may be equal to the maximum targetIoT value, the range of the target IoT value may be determined by theminimum IoT value, and the IoT_(tar) value of each frequency partitionmay be determined by the value of γ. In order to reduce transmissionoverhead of the γ value, the transmitting end and the receiving end cansignal the γ value using a table of the γ value according to a bitsequence and the number of bits required for signaling the γ value andthe table can be appropriately changed according to the systemcharacteristics. The following are examples of the table and the numberof bits required for signaling the γ]value.

IoT_(tar)=(1−γ)IoT_(min)+γIoT_(default) and IoT_(min) can be signaledusing 4 bits for each cell or sector, IoT_(default) can be signaledusing 4 bits for each cell or sector, and γ can be signaled using 2 bitsfor each frequency partition.

In the case where the number of frequency partitions is 4, IoT_(default)can be signaled as “IoT_(default)=0111” if IoT_(default)=7 dB andIoT_(min) can be signaled as “IoT_(min)=0100” if IoT_(default)=4 dB. Inaddition, γ_(FP0), γ_(FP1), γ_(FP2), and γ_(FP3) can be signaled as“γ_(FP0)=00”, “γ_(FP1)=01”, “γ_(FP2)=10”, and “γ_(FP3)=11” if γ_(FP0)=0,γ_(FP1)=1/3, γ_(FP2)=2/3, and γ_(FP3)=1, respectively. This can berepresented by the following Table 1.

TABLE 1 Bit Value 00 0 01 ⅓ 10 ⅔ 11 1

Unlike the first method, in a second method, γ and η may be used inorder to set a target IoT for each frequency partition. That is, it ispossible to set a target IoT for each frequency partition as a ratiowith respect to the default target IoT value using γ and η in the caseof the second method. This method can be represented by the followingMathematical Expression 9.

$\begin{matrix}{{IoT}_{tar} = {\frac{\gamma}{\eta}{IoT}_{default}}} & \left\lbrack {{Mathematical}\mspace{14mu} {Expression}\mspace{14mu} 9} \right\rbrack\end{matrix}$

A list that is signaled by the BS may include a default target IoT(IoT_(default)), an IoT adjustment value γ, and an IoT adjustment valueη where 0≦γ≦1 and 0≦η≦1.

For example, it may be possible that the number of frequency partitionsis 4, IoT_(default)=5 dB, IoT_(target) _(—) _(FP0)=4 dB, IoT_(target)_(—) _(FP1)=5 dB, IoT_(target) _(—) _(FP2)=6 dB, and IoT_(target) _(—)_(FP3)=7 dB, γ_(FP0)=0.4, γ_(FP1)=0.5, γ_(FP2)=0.6, and γ_(FP3)=0.7, andη_(FP0)=0.5, η_(FP1)=1, η_(FP2)=0.5, and η_(FP3)=0.5.

Unlike the first method, the values γ and η may be mapped to appropriatevalues according to a bit sequence using a predefined table bytransmitting and receiving ends in order to reduce signaling overhead.The same table can be used for mapping of γ and η values and the tableand the number of bits required for signaling can be appropriatelychanged according to system characteristics. The number of bits requiredto set a target IoT value for each frequency partition using the γ and ηvalues and the default IoT value can be represented by the followingTable 2. Table 2 is a table for γ and η.

TABLE 2 Bit Value 000 0.2 001 0.3 010 0.4 011 0.5 100 0.6 101 0.7 1100.8 111 0.9

${IoT}_{tar} = {\frac{\gamma}{\eta}{IoT}_{default}}$

and IoT_(default) can be signaled using 4 bits for each cell or sector,and γ can be signaled using 3 bits for each frequency partition, and ηcan be signaled using 3 bits for each frequency partition.

In the case where the number of frequency partitions is 4, IoT_(default)can be signaled as “IoT_(default)=0101” if IoT_(default)=5 dB, andγ_(FP0)=0.4, γ_(FP1)=0.5, γ_(FP2)=0.6, and γ_(FP3)=0.7 can be signaledas “γ_(FP0)=010”, “γ_(FP1)=011”, “γ_(FP2)=100”, and “γ_(FP3)=101”, andη_(FP0)=0.5, η_(FP1)=1, η_(FP2)=0.5, and η_(FP3)=0.5 can be signaled as“η_(FP0)=011”, “η_(FP1)=011”, “η_(FP2)=011”, and “η_(FP3)=011”.

In the case of the second method, in order to reduce signaling overheadthat may be caused when γ and η values are used to set the target IoTfor each frequency partition, the γ value alone can be used as a scalingfactor for the default IoT value, and the IoT of each partition can beadjusted as in the following example.

$\begin{matrix}{{IoT}_{tar} = {\frac{\gamma}{\left( {1 - \gamma} \right)}{IoT}_{default}}} & \left\lbrack {{Mathematical}\mspace{14mu} {Expression}\mspace{14mu} 10} \right\rbrack\end{matrix}$

A list that is signaled by the BS may include a default target IoT(IoT_(default)) and an IoT adjustment value γ (0≦γ≦1).IoT_(tar)=IoT_(default) if γ=1.

For example, when the number of frequency partitions is 4, it may bepossible that IoT_(default)=5 dB, IoT_(target) _(—) _(FP0)=4 dB,IoT_(target) _(—) _(FP1)=5 dB, IoT_(target) _(—) _(FP2)=6 dB, andIoT_(target) _(—) _(FP3)=7 dB, and γ_(FP0)=4/9, γ_(FP1)=1, γ_(FP2)=6/11,and γ_(FP3)=7/12.

Unlike the first and second methods, the value γ may be mapped toappropriate values according to a bit sequence using a table predefinedby transmitting and receiving ends in order to reduce overhead due tosignaling of the adjustment value of the IoT default value. The tableand the number of bits required for signaling can be appropriatelychanged according to system characteristics.

In a fourth method, a scaling factor for a default IoT value is not usedto set the target IoT value of each frequency partition and instead thetarget IoT value of each frequency partition may be set to a valueobtained by increasing or decreasing the default IoT value. This methodcan be represented by the following Mathematical Expression 11.

IoT_(tar)=γ+IoT_(default)   [Mathematical Expression 11]

A list that is signaled by the BS may include a default target IoTIoT_(default) (default target IoT=minimum target IoT) and an IoTadjustment value γ.

For example, when the number of frequency partitions is 4, it may bepossible that IoT_(default)=4 dB, IoT_(target) _(—) _(FP0)=4 dB,IoT_(target) _(—) _(FP1)=5 dB, IoT_(target) _(—) _(FP2)=6 dB, andIoT_(target) _(—) _(FP3)=7 dB, and γ_(FP0)=0, γ_(FP1)=1, γ_(FP2)=2, andγ_(FP3)=3.

The following is an example of a method for setting an target IoT foreach partition to a value obtained by increasing the default IoT and amethod for signaling the target IoT. IoT_(default) can be signaled using4 bits for each cell or sector and γ can be signaled using 2 bits foreach frequency partition. IoT_(default) may be signaled asIoT_(default)=0100 and γ may be signaled as γ_(FP0)0=000 (0 dB),γ_(FP1)=001 (1 dB), γ_(FP2)=010 (2 dB), and γ_(FP3)=011 (3 dB).

In a fifth method, a target IoT value of each partition may be directlysignaled as follows without using the default IoT value of eachpartition.

In the case where IoT_(default)=4 dB, IoT_(target) _(—) _(FP0)=4 dB,IoT_(target) _(—) _(FP1)=5 dB, IoT_(target) _(—) _(FP2)=6 dB, andIoT_(target) _(—) _(FP3)=7 dB when the number of frequency partitions is4, they may be represented as IoT_(target) _(—) _(FP0)=0100 (4dB)[Mathematical, IoT_(target) _(—) _(FP1)=0101 (5 dB), IoT_(target)_(—) _(FP2)=0110 (6 dB), and IoT_(target) _(—) _(FP3)=0111 (7 dB).

In a sixth method, an target IoT value can be set by using the γ valueas a weight factor of the default IoT value for adjusting the target IoTvalue, this can be represented by the following Mathematical Expression12.

IoT_(tar)=γ·IoT_(default)   [Mathematical Expression 12]

Here, a list that is signaled by the BS may include a default target IoT(IoT_(default)) and an IoT adjustment value γ.

In the case where the number of frequency partitions is 4, it may bepossible that IoT_(default)=10 dB, IoT_(target) _(—) _(FP0)=9 dB,IoT_(target) _(—) _(FP1)=10 dB, IoT_(target) _(—) _(FP2)=11 dB, andIoT_(target) _(—) _(FP3)=12 dB, and γ_(FP0)=0.9, γ_(FP1)=1, γ_(FP2)=1.1,and γ_(FP3)=1.2.

The number of bits required for the default IoT value and the target IoTvalue and the table for mapping as represented in the following Table 3can be appropriately changed according to system characteristics. Thiscan be represented by the following Table 3.

TABLE 3 bit Value 0000 0.0 0001 0.1 0010 0.2 0011 0.3 0100 0.4 0101 0.50110 0.6 0111 0.7 1000 0.8 1001 0.9 1010 1.0 1011 1.1 1100 1.2 1101 1.31110 1.4 1111 1.5

In Table 3, IoT_(default) can be signaled using 4 bits for each cell orsector and γ can be signaled using 4 bits for each frequency partition.In the case where the number of frequency partitions is 4, IoT_(default)can be signaled as IoT_(default)=1010 if IoT_(default)=10 dB, andγ_(FP0)=0.9, γ_(FP1)=1, γ_(FP2)=1.1, and γ_(FP3)=1.2 can be signaled asγ_(FP0)=1001, γ_(FP1)=1001, γ_(FP2)=1010, and γ_(FP3)=1100,respectively.

The main concept of open-loop power control is to set transmission powerof the MS. More specifically, transmission power that can achieve atarget SINR is set based on a Modulation and Code Scheme (MCS) indicatedby a control channel (for example, an Advanced-MAP Information Element(A-MAP IE)). Here, the A-MAP IE is briefly described as follows. Controlchannels may include a broadcast channel and an A-MAP IE. The BS maytransmit MCS level information or the like through an A-MAP IE amongcontrol channels. The BS may also transmit resource allocationinformation, power control information, or the like using an A-MAP IE.In many cases, an A-MAP IE is transmitted being coded more strongly thana MAC message.

In order to include new features suitable for the IEEE 802.16m system,open-loop power control suggested in the present invention may controluplink transmission power according to the number of streams to supportuplink Collaborative Spatial Multiplexing (CSM) or single user spatialmultiplexing. According to this modification, the total amount ofinterference to a neighbor cell can be fixed regardless of the number ofstreams used. Open-loop power control according to the present inventioncan control transmission power of an MS so that the estimated IoT leveldoes not exceed the target value. In addition, the suggested IoT controlcan be efficiently combined with the FFR scheme.

The following Mathematical Expression 13 is an example of an open-looppower control formula suggested in the present invention.

P _(Tx)=min(P _(Tx,1) , P _(Tx,2)) [dBm]  [Mathematical Expression 13]

Here, P_(Tx,1)=PL_(s)+NI+SINR_(Target)+Offset_(perAMS)+Offset_(perABS)[dBm] and P_(Tx,2)=TargetIoT+N₀+PL_(i) [dBm],P_(Tx,2)=TargetIoT+N₀+SIR+PL_(s) [dBm],P_(Tx,2)=TargetIoT+N₀+SINR+PL_(s) [dBm] P_(Tx,2)=NI+SIR+PL_(s) [dBm],P_(Tx,2)=TargetIoT+NI+PL_(s)+SINR, or P_(Tx,2)=TargetIoT+N₀−10 log10(P_(RX)/P_(Tx) ^(DL)−10^(−PL) ^(s) ^(/10))[dBm]. In all of thesecases, the target IoT can be replaced with an arbitrary controllingparameter that is signaled to the MS in order to control inter-cellinterference (or IoT). A different value may be signaled in eachfrequency partition (or band).

Here, PL_(s) denotes pathloss for a serving BS, PL_(i) denotes pathlossfor a BS with the strongest interference, P_(Rx) denotes total receptionpower, P_(Tx) ^(DL) denotes transmission power of the BS, NI denotes anoise and interference level of the serving cell that is updated every100 ms, N₀ denotes noise power density, SINR_(Target) may mean afunction of an MCS and a target Block Error Rate (BLER) (i.e.,SINR_(Target)=f(MCS, targetBLER)), and Offset_(perAMS) may denotes acorrection term for a specific-MS power offset. Offset_(perABS) may be atransmission power level adjustment value controlled by the MS. The MScan perform mode switching between open-loop power control andclosed-loop power control using a power control message through a ULA-MAP.

The above Mathematical Expression 13 can be changed to the followingMathematical Expression 14 or 15.

P _(Tx)=min(P _(Tx,1) ,P _(TX,2))−10 log 10(MT _(T))[dBm]  [MathematicalExpression 14]

P _(Tx)=min(P _(Tx,1) ,P _(Tx,2)−10 log 10(MT _(T)))[dBm]  [MathematicalExpression 15]

Here, P_(Tx) denotes transmission power of each stream and eachsubcarrier and MT_(T) denotes the total number of streams for acorresponding resource unit indicated by a UL A-MAP IE. P_(Tx)+10log(10*(the total number of subcarriers in the frequency domain for eachOFDMA symbol)) cannot exceed the maximum transmission power of the MS.The BS can transmit TargetIoT to the MS through a control channel orusing message type. Here, TargetIoT may be signaled to an MS through asuperframe header (for example, a Secondary Superframe Header (S-SFH) orAdditional Broadcast Information (ABI)) in the control channel and mayalso be signaled to a specific MS through a unicast or the like. The MSmay perform power control so that interference to another sector doesnot exceed the signaled TargetIoT. Here, TargetIoT may differ in eachfrequency partition. In the case of a Single-Input Multi-Output (SIMO)simulation, MT_(T) can be set to “1”.

An example procedure in which a BS determines a TargetIoT level isdescribed as follows.

Each BS may calculate IoT_(avg) and the network may calculate a mean IoTvalue by averaging the IoT_(avg) levels of BSs. The network thencompares the averaged mean IoT with a desired IoT level. Here, thedesired IoT level is a common mean IoT level that the network desiresall BSs to have. TargetIoT is reduced if the averaged mean IoT value isgreater than the desired IoT level and is increased if the mean IoTvalue is less than the desired IoT level. Thereafter, the BS can signalthe updated TargetIoT level. This procedure may be periodicallyrepeated.

Another example procedure for determining the TargetIoT level isdescribed as follows. BSs exchange desired IoT levels. Here, each BS maydesire a different IoT level. Thereafter, each BS calculates TargetIoTtaking into consideration a desired IoT level received from another BS.Then, the BS broadcasts the updated TargetIoT level. This procedure maybe periodically repeated.

The following Mathematical Expression 16 represents uplink open-looppower control of the IEEE 802.16e system.

P _(tx) =PL+NI+SINR_(target)+Offset_(perAMS)+Offset_(perABS)  [Mathematical Expression 16]

A method for improving system performance, controlling inter-cellinterference, and improving cell-edge user performance based on thisequation can be implemented in a unified algorithm form. The suggestedmethod described below is based on single stream transmission. Onemethod for extending the single stream to multiple streams is to add‘−10 log₁₀(MT_(T))’ to a finally determined value or an appropriateintermediate value.

This serves to reduce the amount of interference in a multiple userenvironment having multiple streams with the same resource to aninterference level of a single user environment having a single streamwith one resource, thereby improving performance. This may operate basedon a minimum amount of control information.

Power that is to be transmitted by an MS taking into considerationinter-cell interference and cell-edge users in the first method amongthe uplink open-loop power control methods can be represented by thefollowing Mathematical Expressions 17.

P _(tx) =PL ₁ +NI+(SINR _(target), max(SINR_(min),min(SINR_(target),ΔIoT_(max)+N₀+SIR_(DL))))+Offset_(perAMS)+offset_(perABS)−10log₁₀(MT_(T))   [Mathematical Expression 17]

P _(tx) =PL _(s) +NI+(SINR_(target), max(SINR_(min), min(SINR_(target),ΔIoT_(max) +N ₀+SIR_(DL)−10 log₁₀(MT_(T)))))+Offset_(perAMS)+Offset_(perABS)   [Mathematical Expression 18]

P _(tx) =PL _(s) +NI+(SINR_(target), max(SINR_(min),min(SINR_(target),ΔIoT_(max) +N₀+SIR_(DL))+Offset_(perAMS)+Offset_(perABS)))−10 log₁₀(M _(T))  [Mathematical Expression 19]

P _(tx) =PL _(s) +NI+(SINR_(target), max(SINR_(min), min(SINR_(target),ΔIoT_(max) N ₀+SIR_(DL)−10 log₁₀(MT_(T)))+Offset_(perAMS)+Offset_(perABS))   [Mathematical Expression 20]

ΔIoT_(max)=IoT_(max) −NI   [Mathematical Expression 21]

In the first method, a parameter which serves as an SINR target valuehas two options. Initially, the BS may determine a transmission controlmode of the MS or the MS may request a specific mode from the BS asrepresented by (SINR_(target), max(SINR_(min),min(SINR_(target),ΔIoT_(max)+N₀+SIR_(DL)))). The step of determining theinitial target value if it is not an SINR target value is represented bymax(SINR_(min), min(SINR_(target),ΔIoT_(max)+N₀+SIR_(DL))).

In Mathematical Expression 18, transmission power is determined through2 steps in a method of determining a Power Spectral Density (PSD) level.Mathematical Expressions 17, 18, and 19 may be classified according tothe positions of two parameters that are identified as offsets.Mathematical Expressions 18 and 19 may be classified according to theposition of MT_(T). Mathematical Expressions 20 and 21 may also beclassified using the same concept. Here, a multi-stream part is used asan element for determining transmission power. In addition to, thefollowing is a description of a method that can be applied to the aboveMathematical Expressions when the FFR scheme is taken intoconsideration.

The SINR_target value which is commonly applied to MathematicalExpressions 17 to 20 may be equal or different for each frequencypartition.

FIG. 4 illustrates an example wherein a different SINR_target value isapplied in each frequency partition when the FFR scheme is applied.

Referring to FIG. 4, regions F1 and F4 in cell 1 have the sameSINR_target level and regions F2 and F3 have relatively lowerSINR_target levels than F1 and F4. However, the regions F2 and F3 mayhave the same SINR_target value or different SINR_target values. In amethod for determining such values, they may be determined on asystem-wide basis at the network level.

A variety of user identification methods or user allocation methods maybe considered. These methods may be based on user geometry, pathloss,reception SINR, and the like. The basic principle of division offrequency partitions is that frequency partitions are divided in acoordinated fashion at the network level. Of course, the number offrequency partitions is not fixed to 4. Even if the number of frequencypartitions is increased, different SINR_target values may be set andused for frequency partitions, which are allowed to be used to besuitable for purposes, as follows:

SINR_target_F1 and F4: 10 dB

SINR_target_F2 and F3: 8 dB

In another example, different SINR_target values may be set forfrequency partitions as follows:

SINR_target_F1: 10 dB

SINR_target_F4: 9 dB

SINR_target_F2 and F3: 8 dB

In another example, different SINR_target values may be set forfrequency partitions as follows:

SINR_target_F1: 10 dB

SINR_target_F4: 9 dB

SINR_target_F2: 8 dB

SINR_target_F2: 7 dB

As different SINR_target values may be set for frequency partitions,SINR_(min) or SIR_(min) values, which are commonly used in the aboveMathematical Expressions 17 to 20, can also be set differently forfrequency partitions. The same level of values may be used in frequencypartitions or may be used as in the following examples. However, it ispreferable that SINR_target values be set to be suitable for thesituation of the system.

In an example, SINR_target values may be set for frequency partitions asfollows:

SINR_min_F1, F2 and F3: 0 dB

SINR_min_F4: −∞

In another example, SINR_target values may be set for frequencypartitions as follows:

SINR_min_F1: 0 dB

SINR_min_F4: 3 dB

SINR_min F2 and F3: −1 dB

In another example, SINR_target values may be set for frequencypartitions as follows:

SINR_min_F1: 0 dB

SINR_min_F4: 3 dB or −∞

SINR_min_F2: −1 dB

SINR_min_F2: −2 dB

Alternatively, the same value may be set for frequency partitions asfollows: SINR_min_F1, F2, F3 and F4: 0 dB. The value of ΔIoT_(max),which is commonly used in the above Mathematical Expressions 17 to 20,may also be set to be different for each frequency partition. Forexample, the values of ΔIoT_(max) of the frequency partitions F1 and F4may be set to be relatively greater than those of the frequencypartitions F2 and F3.

In the second method among the open-loop power control methods in whichan MS controls transmission power, SINR_(min) and ΔIoT_(max)+N₀+SIR_(DL)values are compared directly with each other and the greater of thesetwo values is used in place of the SINR_(target) value in the case ofmodes other than the mode in which the SINR_(target) value is selected.Equations for obtaining transmission power based on the second methodcan be represented in a variety of forms as in Mathematical Expressions22 to 25.

P _(tx) =PL _(s) +NI+(SINR_(target), max(SINR_(min),ΔIoT_(min) +N₀+SIR_(DL)))+Offset_(perAMS)+Offset_(perABS)−10 log₁₀(MT _(T))  [Mathematical Expression 22]

P _(tx) =PL _(s) +NI+(SINR_(target), max(SINR_(min),ΔIoT_(min) N₀+SIR_(DL))−10 log₁₀(MT _(T)))+Offset_(preAMS)+Offset_(ABS)  [Mathematical Expression 23]

P _(tx) =PL _(s) +NI+(SINR_(target), max(SINR_(min) +ΔIoT _(mn) +N₀+SIR_(DL))+Offset_(perAMS)+Offset_(perABS))−10 log₁₀(MT _(T))  [Mathematical Expression 24]

P _(tx) =PL _(s) +NI+(SINR_(target), max(SINR_(min)ΔIoT_(min) +N₀+SIR_(DL)−10 log₁₀(MT _(T)))+Offset_(perAMS)+Offset_(perABS))  [Mathematical Expression 25]

The equations based on the second method are divided into MathematicalExpressions 22 to 25 for the same reason as why the equations based onthe first method are divided into Mathematical Expressions 17 to 20.Here, SINR_(target), ΔIoT_(max), SINR_(min), or SIR_(min) values mayeach be set to be different for each frequency partition.

In a third method, P_(min), P_(tx1) and P_(tx2) are compared with eachother to determine P_(tx). This can be represented by the followingMathematical Expressions 26 to 29.

P _(tx)=max[P _(min), min(P _(tx1) ,P _(tx2))]  [Mathematical Expression26]

P _(min)=SINR_(min) +NI+PL _(s)   [Mathematical Expression 27]

P _(tx1)=SINR_(tar) +NI+PL _(s)+Δoffset_(MS)+Δoffset_(BS)  [Mathematical Expression 28]

P _(tx2)=IoT_(max) +PL _(s) +N ₀+SIR−10 log₁₀ (MT _(T)) (MT_(T)=1)  [Mathematical Expression 29]

Here, P_(tx1) is equal to that of Mathematical Expression 16 and P_(tx2)can be considered to play the same role as ΔIoT_(max)+N₀+SIR_(DL)Mathematical Expressions 17 to 20 when MT_(T)=1.

PL_(s) denotes pathloss estimated by MS for the serving cell, PL_(i)denotes pathloss estimated by MS for a cell with the strongestinterference, NI denotes estimated an average power level of noise andinterference of each subcarrier in the serving cell, and SINR_(target)denotes an SINR level for transmitting a data or control channel.SINR_(min) is the minimum SINR value given by the serving BS.Offset_(perAMS) denotes a correction term for a specific-MS poweroffset. The MS can perform mode switching between open-loop powercontrol and closed-loop power control using a power control messagethrough a UL A-MAP. Offset_(perABS) is a transmission power leveladjustment value that is controlled by the MS. MT_(T) denotes the totalnumber of streams indicated by a UL A-MAP IE. In the case of single-userMIMO, the value of MT_(T) is set to M_(t), which is the number ofstreams of each user. In the case of CSM, the value of MT_(T) is set toM_(t) _(—) _(A), which is the total number of streams. In the case ofcontrol channel transmission, the value of MT_(T) may be set to 1. TheBS may broadcast the target IoT level to another sector through anS-SFH. Here, the target IoT level may be different for each frequencypartition.

A fourth method is described as follows. Both power of each subcarrierand power for each transmit antenna in open-loop power control aremaintained by uplink transmission represented by the followingMathematical Expression 30.

P(dBm)=L+SINR_(Target) +NI+OffsetAMS_(perAMS)+OffsetABS_(perAMS)  [Mathematical Expression 30]

Here, SINR_(target) is a target uplink SINR value received from a BS. Amode that is used to calculate this value may be signaled through apower control message. P is a transmission power level (dBm) persubcarrier for current transmission and L is an estimated averagecurrent uplink propagation loss. L may include a transmit antenna gainand pathloss of the MS. NI is an average power level of noise andinterference per subcarrier estimated in the BS and does not include areceive antenna gain of the BS. OffsetAMS_(perAMS) is a correction termfor a specific-MS power offset and is controlled by the BS.OffsetABS_(perABS) is a correction term for a specific-MS power offsetand is controlled by the BS. The estimated average current uplinkpropagation loss L can be calculated based on total power received in anactive subcarrier of a preamble.

When a user connects to the network, it is possible to performnegotiation of parameters using the following Mathematical Expression31.

$\begin{matrix}{\mspace{405mu} \left\lbrack {{Mathematical}\mspace{14mu} {Expression}\mspace{14mu} 31} \right\rbrack} \\{{SINR}_{Target} = \left\{ \begin{matrix}{{SINR}_{OPT},} & {{OLPC}\mspace{14mu} {Mode}\mspace{14mu} 1} \\{\left( {{C/N} - {10\log \; 10(R)}} \right),} & {{OLPC}\mspace{14mu} {Mode}\mspace{14mu} 2}\end{matrix} \right.}\end{matrix}$

Here, C/N is a normalized C/N of the modulation/FEC rate of the currenttransmission. This value is a parameter associated with an MCS level. Ris the number of repetitions for the modulation/FEC rate. SINR_(OPT) isa target SINR value for trade-off and IoT control between total systemthroughput and cell-edge performance and is determined by a controlparameter γ or Δ_(IoT) and SINR_(min). Here, a different symbol from γor Δ_(IoT) may be used to represent the control parameter. SINR_(OPT)can be represented by the following Mathematical Expression 32.

$\begin{matrix}{\mspace{405mu} \left\lbrack {{Mathematical}\mspace{14mu} {Expression}\mspace{14mu} 32} \right\rbrack} \\{{{SINR}_{OPT} = {10\log \; 10\left( {\max \left( {10^{\frac{{SINR}_{MIN}}{10}},{{\gamma \cdot {SIR}_{DL}} - \frac{1}{N_{r}}}} \right)} \right)}},{or}} \\{{\max \left( {{SINR}_{MIN},{\min \left( {{{C/N} - {10\log \; 10(R)}},{\Delta_{IoT} + {10\log \; 10\left( {SIR}_{DL} \right)}}} \right)}} \right)}.}\end{matrix}$

Here, SINR_(min) denotes the minimum required SINR expected by the BSand can be set by a unicast power control message. SINR_(min) can beexpressed using 4 bits in units of dB. Δ_(IoT) or γ is a parameter forIoT control signaled by the BS and may have a different value for eachfrequency partition. N_(r) denotes the number of receive antennas in theBS and SIR_(DL)denotes the ratio of downlink signal power tointerference power measured by the MS.

${SINR}_{OPT} = {10\log \; 10\left( {\max \left( {10^{\frac{{SINR}_{MIN}}{10}},{{\gamma \cdot {SIR}_{DL}} - \frac{1}{N_{r}}}} \right)} \right)}$

which is one option in Mathematical Expression 32, SINR_(min) and γ canbe used for uplink open-loop power control. This method can improve thegain when the FFR scheme is applied. The value of γ to be used can beselected from an appropriate range such as {0, 0.1, . . . , 1.0, . . , )and it is possible to efficiently support the FFR scheme if differentselected γ values are applied to frequency partitions.

ΔIoT_(max), SINR_(Target), SINR_(min), IoT_(max), NI, MT_(T), γ may betransmitted from a corresponding BS to MSs through a broadcast channel,a superframe header, ABI, a UL A-MAP IE or a message type. The amount ofthe transmitted information may vary according to the number offrequency partitions. The following are examples in which a BSbroadcasts such information to MSs according to the frequency partition.

$\begin{matrix}\begin{matrix}{\Delta \; {IoTmax\_ FP}\; 0\text{:}\mspace{14mu} {xx}\mspace{14mu} {dB}\mspace{14mu} {or}\mspace{14mu} {Table}\mspace{14mu} {index}} \\{\Delta \; {IoTmax\_ FP}\; 1\text{:}\mspace{14mu} {xx}\mspace{14mu} {dB}\mspace{14mu} {or}\mspace{14mu} {Table}\mspace{14mu} {index}} \\{\Delta \; {IoTmax\_ FP}\; 2\text{:}\mspace{14mu} {xx}\mspace{14mu} {dB}\mspace{14mu} {or}\mspace{14mu} {Table}\mspace{14mu} {index}} \\{\mspace{200mu} \vdots} \\{\Delta \; {IoTmax\_ FP}{\_ last}\text{:}\mspace{14mu} {xx}\mspace{14mu} {dB}\mspace{14mu} {or}\mspace{14mu} {Table}\mspace{14mu} {index}}\end{matrix} \\\begin{matrix}{{SINR}_{Target}{\_ FP}\; 0\text{:}\mspace{14mu} {xx}\mspace{14mu} {dB}\mspace{14mu} {or}\mspace{14mu} {Table}\mspace{14mu} {index}} \\{{SINR}_{Target}{\_ FP}\; 1\text{:}\mspace{14mu} {xx}\mspace{14mu} {dB}\mspace{14mu} {or}\mspace{14mu} {Table}\mspace{14mu} {index}} \\{{SINR}_{Target}{\_ FP}\; 2\text{:}\mspace{14mu} {xx}\mspace{14mu} {dB}\mspace{14mu} {or}\mspace{14mu} {Table}\mspace{14mu} {index}} \\{\mspace{194mu} \vdots} \\{{SINR}_{Target}{\_ FP}{\_ last}\text{:}\mspace{14mu} {xx}\mspace{14mu} {dB}\mspace{14mu} {or}\mspace{14mu} {Table}\mspace{14mu} {index}}\end{matrix} \\\begin{matrix}{{SINR}_{MIN}{\_ FP}\; 0\text{:}\mspace{14mu} {xx}\mspace{14mu} {dB}\mspace{14mu} {or}\mspace{14mu} {Table}\mspace{14mu} {index}} \\{{SINR}_{MIN}{\_ FP}\; 1\text{:}\mspace{14mu} {xx}\mspace{14mu} {dB}\mspace{14mu} {or}\mspace{14mu} {Table}\mspace{14mu} {index}} \\{{SINR}_{MIN}{\_ FP}\; 2\text{:}\mspace{14mu} {xx}\mspace{14mu} {dB}\mspace{14mu} {or}\mspace{14mu} {Table}\mspace{14mu} {index}} \\{\mspace{185mu} \vdots} \\{{SINR}_{MIN}{\_ FP}{\_ last}\text{:}\mspace{14mu} {xx}\mspace{14mu} {dB}\mspace{14mu} {or}\mspace{14mu} {Table}\mspace{14mu} {index}}\end{matrix} \\\begin{matrix}{{NI\_ FP}\; 0\text{:}\mspace{14mu} {xx}\mspace{14mu} {dB}\mspace{14mu} {or}\mspace{14mu} {Table}\mspace{14mu} {index}} \\{{NI\_ FP}\; 1\text{:}\mspace{14mu} {xx}\mspace{14mu} {dB}\mspace{14mu} {or}\mspace{14mu} {Table}\mspace{14mu} {index}} \\{{NI\_ FP}\; 2\text{:}\mspace{14mu} {xx}\mspace{14mu} {dB}\mspace{14mu} {or}\mspace{14mu} {Table}\mspace{14mu} {index}} \\{\mspace{185mu} \vdots} \\{{NI\_ FP}{\_ last}\text{:}\mspace{14mu} {xx}\mspace{14mu} {dB}\mspace{14mu} {or}\mspace{14mu} {Table}\mspace{14mu} {index}}\end{matrix} \\\begin{matrix}{{\gamma\_ FP}\; 0\text{:}\mspace{14mu} {xx}\mspace{14mu} {dB}\mspace{14mu} {or}\mspace{14mu} {Table}\mspace{14mu} {index}} \\{{\gamma\_ FP}\; 1\text{:}\mspace{14mu} {xx}\mspace{14mu} {dB}\mspace{14mu} {or}\mspace{14mu} {Table}\mspace{14mu} {index}} \\{{\gamma\_ FP}\; 2\text{:}\mspace{14mu} {xx}\mspace{14mu} {dB}\mspace{14mu} {or}\mspace{14mu} {Table}\mspace{14mu} {index}} \\{\mspace{169mu} \vdots} \\{{\gamma\_ FP}{\_ last}\text{:}\mspace{14mu} {xx}\mspace{14mu} {dB}\mspace{14mu} {or}\mspace{14mu} {Table}\mspace{14mu} {index}}\end{matrix}\end{matrix}$

Here, the transmission period of the above parameter values from the BSto the MS may be fixed or changed freely. Upon receiving the parametervalues, the MS may determine transmission power based on the receivedparameter values. In one parameter notification method, the BS maynotify the MS of each parameter value in a form such as a real value, amapping value of a predefined table, or the like.

The following is a description of a detailed signaling method in which aBS signals information required for transmission power controlled by theMS.

FIG. 5 illustrates the operation of a soft FFR scheme in downlink.

Referring to FIG. 5, in downlink, a BS may cause interference while anMS may be influenced by interference. The BS, which causes interferencein downlink, may set a transmission power level for each FFR group (orpartition). One BS may signal information of the transmission powerlevel set for each FFR partition to another BS using a backbone networkor the like. BSs may share the information of the transmission powerlevel set for each FFR partition. Each BS may signal the information ofthe transmission power level set for each FFR partition to the MS. Inthe IEEE 802.16m system, such transmission power level set informationmay be periodically broadcast in units of a superframe or multiplesuperframes to each MS. Such information may also be implicitlytransmitted through a reference signal (for example, a preamble). Thismay indicate that the reference signal is transmitted as thetransmission power level for each FFR partition.

FIG. 6 illustrates an example operation scenario of a BS and an MS whena soft FFR scheme is applied in uplink.

Referring to FIG. 6, the BS may set a maximum transmission power levelof an MS or a highest Modulation and Coding Schemes (MCS) level, aspecific parameter value used when the MS controls transmission power,for each FFR group (or partition). One BS may signal information of themaximum transmission power level of the MS or the specific parametervalue or highest MCS level for transmission power control of the MS setfor each FFR group to another BS using the backbone network. BSs mayshare the information of the maximum transmission power level of the MSor the specific parameter value or highest MCS level for control oftransmission power of the MS set for each FFR group.

Each BS may signal, to the MS, the set information of the maximumtransmission power level of the MS or the specific parameter value orhighest MCS level for control of transmission power of the MS. Such setinformation may be periodically broadcast in units of a superframe ormultiple superframes to each MS. Such information may also be signaledto the MS in an ABI or message type. The information signaled to the MSmay be used for uplink power control.

FIG. 7 illustrates an example operation scenario of a BS and an MS whena soft FFR scheme is applied in uplink.

Referring to FIG. 7, a BS, which is influenced by interference inuplink, may set a target IoT level (or IoT control parameter) for eachFFR group (or partition). Here, the IoT level is a value indicating thedegree of interference between cells. One BS may signal information ofthe target IoT level set for each FFR partition to another BS using abackbone network. BSs may share the information of the degree ofinterference for each FFR partition. Each BS may signal the informationof the degree of interference for each FFR partition and the informationof the target IoT level for each FFR partition shared between BSs to theMS.

The signaled information of the degree of interference for each FFRpartition and the signaled information of the target IoT level for eachFFR partition may be used for Open Loop Power Control (OLPC) or may beimplicitly used for Closed Loop Power Control (CLPC). Each BS mayperiodically broadcast the target IoT level information to the MS inunits of a superframe or multiple superframes, which are defined in theIEEE 802.16m system, to each MS. The BS may also transmit the target IoTlevel information to the MS in an ABI or message format.

FIG. 8 illustrates duality of a downlink transmission power level and anuplink target IoT level.

In downlink, a BS, which causes interference, may signal a transmissionpower level to an MS after negotiation between BSs. In this Case, the MSmay be influenced by interference. However, in uplink, since the MScauses interference, the BS, which is influenced by interference, maysignal a target IoT level to the MS after negotiation between BSs. Asshown in FIG. 8, the uplink target IoT level is low in a frequency reuseregion with a high downlink transmission power level and is high in afrequency reuse region with a low downlink transmission power level.Thus, it can be considered that the downlink transmission power leveland the uplink target IoT level are in a dual relation.

In the above operation scenario, all cells may have the same FFRconfiguration information. The FFR configuration information may includethe number of FFR groups and the respective bandwidths of the groups. Inthe IEEE 802.16m system, the BS may transmit an FFR configurationinformation to the MS through a broadcast channel in units of asuperframe or multiple superframes. The BS may also transmit a targetIoT level of each FFR group as a part of the FFR configuration to theMS. In uplink power control, the target IoT level may be replaced withinterference information of each FFR group. The MS may use the targetIoT level information received from the BS for power control. Here,information of the degree of interference of each FFR group may beshared between BSs and may be signaled to the MS to be used foropen-loop power control or may be implicitly used for open-loop powercontrol. The MS may additionally use information of geometry withrespect to a neighbor BS for power control. That is, when performingpower control, the MS may use both the FFR group and IoT level controlin the following manner. The MS may perform power control using thetarget IoT level of each FFR group, the degree of interference of eachFFR group, and information of pathloss to a neighbor BS (i.e.,P_MS=P_intra−f(the target IoT level of each FFR group, the degree ofinterference of each FFR group, and pathloss to neighbor BS)).Alternatively, the MS may perform power control using the target IoTlevel of each FFR group, the degree of interference of each FFR group,pathloss to a neighbor BS, and pathloss to the serving BS (i.e.,P_MS=f(the target IoT level of each FFR group, the degree ofinterference of each FFR group, pathloss to neighbor BS, and pathloss toserving BS)). Here, P_MS denotes power of the MS and P_intra denotespower adjusted by power control in the same cell.

It is preferable that inter-cell interference be taken intoconsideration when the MS controls uplink power. In order to provideInterference plus Noise Ratio (SINR) or a Carrier to Interference plusNoise Ratio (CINR) required for receiving a signal and data withouterrors at the receiver side, the transmitter may determine transmissionpower taking into consideration pathloss, noise and interference, and atarget SINR or CINR desired by the receiver side. Here, transmissionpower can be represented by P_(tx)=SINR_(t)+(N+I)+PL.

The transmission power set in this manner may be calculated asP_(tx)=min{P_(max), SINR_(t)+(N+I)+PL_(s)+offset}, taking intoconsideration an offset value and a maximum transmission power dependenton system characteristics. However, in this power control method inmulti-cell (sector) environments, P_(max) that is commonly applied toall transmitters, an offset value, pathloss (PL), and noise (N) andinterference (I) that have been set without taking into considerationInter-Cell Interference may cause or increase ICI to a neighbor cell.This not only may cause a deterioration of system performance but mayalso cause restriction of system coverage and the capacity. A powercontrol method, in which PL items to be compensated are controlledtaking into consideration ICI, (for example,P_(tx)=SINR_(t)+(N+I)+scale_factor(PL_(s))) has a problem in that atradeoff occurs between cell (sector)-edge user performance and centeruser performance. Accordingly, there is a need to provide a new powercontrol method to overcome such problems.

In multi-cell (sector) environments, transmission power of one cell orsector may operate as interference power for a receiver of another cell(sector). Inter-cell interference may be effectively controlled byapplying a factor such as IoT, in which inter-cell interference isreflected, when transmission power is set. Inter-cell interference maybe controlled by comparing a value of inter-cell interference that iscaused to a neighbor cell by transmission power with a specific value ora threshold value and then increasing or decreasing transmission powerbased on the comparison.

It is preferable that, if the level of interference or the level of IoTto a neighbor cell estimated using transmission power calculated throughpower control of the same cell or transmission power calculated withoutusing the factor, in which inter-cell interference is reflected, ishigher than the threshold value, transmission power be increased so thatthe level of interference or the level of IoT caused to the neighborcell does not exceed the threshold value. Alternatively, link qualitymay be improved by increasing, if the level of interference or the levelof IoT is less than the threshold value, transmission power within arange in which the level of interference or the level of IoT does notexceed the threshold value. Here, transmission power may also be useddirectly without increasing the transmission power.

The threshold of the interference level or IoT level, which the BS usesto determine transmission power, may be set to one value for allfrequency bands. The threshold may also be set for each frequency band,each frequency partition, or each frequency band allocated to the MS.The BS may use a predefined value according to system characteristics asthe threshold and may also adaptively set the threshold using a valueexchanged between cells through a wireless channel or the backbonenetwork.

When the threshold of the IoT level is exchanged between neighbor cells,this value may or may not be quantized. An index or indicator, whichindicates the predefined value, may also be used. A power control methodthat uses the factor such as the IoT value in which inter-cellinterference is reflected may control transmission power by increasingor decreasing transmission power calculated by power control in the samecell (i.e., intra-cell power control, without taking into considerationinter-cell interference). Alternatively, transmission power may becontrolled by increasing or decreasing transmission power calculatedusing the factor such as the IoT value, in which inter-cell interferenceis reflected, according to power control in the same cell.

The following is an example of a method for controlling uplink power.

Inter-cell interference can be reduced by applying an open-loop schemeor a closed-loop scheme to uplink transmission power control in thefollowing manner using an IoT value in which the degree of inter-cellinterference is reflected.

First, initial (intra-cell) transmission power can be calculated. Thefollowing Mathematical Expression 32 is an equation for calculating theinitial transmission power.

P _(tx)=min{P _(max), SINR_(t)+(N+I)+F·PL _(s)}(dB)   [MathematicalExpression 32]

Here, P_(tx) denotes transmission power, P_(max) denotes maximumtransmission power, SINR_(t) denotes a target SINR, N denotes thermalnoise, I denotes interference, F denotes a scaling factor, and PL_(s)denotes pathloss between an MS and a serving BS.

Thereafter, an IoT value of a neighbor cell can be estimated. Theestimated neighbor cell IoT value can be represented by the followingequation.

$\begin{matrix}{{P_{ici} = {P_{tx} - {{PL}_{i,{BS}}\mspace{14mu} ({dB})}}},{{IoT}_{est} = \frac{\left( {N + P_{ici}} \right)}{N}}} & \left\lbrack {{Mathematical}\mspace{14mu} {Expression}\mspace{14mu} 34} \right\rbrack\end{matrix}$

Here, P_(ici) denotes inter-cell interference power, P_(tx) denotestransmission power, PL_(i,BS) denotes pathloss between an MS and aninterference cell BS, and IoT_(est) denotes an estimated IoT value.

Thereafter, transmission power can be controlled by comparing theestimated IoT value and the threshold IoT value. Transmission power canbe adjusted if the estimated IoT value is greater than the threshold IoTvalue. In the case where the IoT value applied to a neighbor cell due totransmission power is greater than the threshold IoT value, transmissionpower can be adjusted so that the IoT value does not exceed thethreshold IoT value. That is, transmission power can be adjusted asrepresented by P_(tx)=(IoT_(thr)×N)−N+PL_(i,BS). On the other hand, inthe case where the IoT value applied to a neighbor cell due totransmission power is less than the threshold IoT value, a valuecalculated through power control in the same cell (i.e., intra-cellpower control) can be used as uplink transmission power.

In addition, if the newly calculated transmission power value is lessthan a transmission power value required in a predefined MCS level inthe case where the estimated IoT value is greater than the threshold IoTvalue, the BS or MS may apply modulation and coding to the MCS levelcorresponding to the newly calculated transmission power. Accordingly,it is possible to improve link reliability and to reduce interference inthe same cell. It is possible to signal the reduced transmission poweror MCS level or a corresponding factor to the BS or MS so that the BS orMS can recognize it.

Also, in the case where the estimated IoT value is less than thethreshold IoT value, a transmission power value calculated through powercontrol in the same cell is allowed to be increased so as to achieve anMCS level higher than the set MCS level within a range in which the IoTvalue does not exceed the threshold IoT value, the BS or MS can applymodulation and coding to the MCS level corresponding to the increasedtransmission power. Here, it is possible to signal the increasedtransmission power or MCS level or a corresponding factor to the BS orMS so that the BS or MS can recognize it.

Referring to the determination of the threshold IoT value, in powercontrol using the IoT value, the threshold IoT value may be set to onevalue or multiple values according to a frequency partition. In the caseof a system using an FFR scheme, when scheduling is performed such thata cell-edge user or a center user of another cell uses the samefrequency partition (a partition of frequency reuse factor 1/N) or thata center user of one cell or a center user of another cell uses the samefrequency partition (a partition of frequency reuse factor 1), thethreshold IoT value of the cell-edge user may be set to be higher thanthat of the cell center user in the band partition of frequency reusefactor 1/N.

The threshold IoT value of the cell center user may be set to be lowerthan that of the cell-edge user. On the other hand, the threshold IoTvalues applied to the cell-edge user and the center user may be set tobe equal according to system characteristics and conditions. Thethreshold IoT values set in this manner may be adaptively changedthrough broadcasting or signaling between BSs according to systemenvironments.

The BS measures an IoT value upon receiving a NACK signal indicatingthat the channel condition is bad from the MS. When the BS has receiveda NACK signal more than a predefined number of times, the BS may notifya neighbor BS of an IoT value upon receiving the NACK signal. Thenotified IoT value may include the average, minimum, maximum, orspecific IoT value of the NACK status. When the BS has received athreshold IoT value from a neighbor BS, the BS may set the threshold IoTvalue to the average, minimum, or maximum of the received IoT value ormay set the threshold IoT value according to a predefined method.

Initial calibration and periodic adjustment of transmission power maysupport uplink power control without data loss. The uplink power controlalgorithm may determine the transmission power of an OFDM symbol inorder to compensate for pathloss, shadowing and fast fading. Such uplinkpower control is designed to control the inter-cell interference level.

A transmitting MS maintains the same transmission power density unlessthe maximum power level is reached. That is, when the number of activeLogical Resource Units (LRUs) allocated to a user is reduced, the totaltransmission power may be reduced by the MS in proportion to the numberof active LRUs without additional power control messages. However, thetransmission power level does not exceed the maximum level indicated bysignal integrity considerations and regulatory requirements. The MS mayinterpret a transmission power control message which indicates arequired change of the transmission power density. In interference levelcontrol, the current IoT level of each cell may be shared among BSs. Inaddition, a parameter for controlling inter-cell interference may bedetermined by coordination between BSs.

FIG. 9 illustrates an example wherein a different transmission powervalue is used for each frequency partition in the case where an uplinkFFR scheme is applied.

Referring to FIG. 9, a system which uses an uplink FFR scheme may have adifferent uplink IoT control parameter (γ_(IoT)) for each frequencypartition. In the case of the uplink FFR scheme, the BS may measureamount of the interference for each frequency partition and may transmitrequired information such as the measured interference information foreach frequency partition to the MS or to another BS. An uplink FFRconfiguration includes information of the size of each frequencypartition and the number of frequency partitions broadcast through asecondary superframe header (S-SFH). The following Table 4 illustratesan S-SFH SP2 IE associated with the uplink FFR scheme.

TABLE 4 Syntax Size (bit) Notes S-SFH SP2 IE format ( ) { Duplexing mode1 Sub-frame configuration (DL/UL 6 ratio. duplexing mode) If (Duplexingmode == FDD) { UL carrier frequency [12]  (Need more discussion) ULbandwidth [3] (Need more discussion) } MSB bytes of BSID 24  Specifiesthe Operator ID FFR partitioning info for DL region [11]  DL_SAC(4).DL_FPSC(3). DL_FPC(4) (Up to 11 bits. Need the decision from DL physicalstructure section) FFR partitioning info for UL region [11]  UL_SAC(4).UL_FPSC(3). UL_FPC(4) (up to 11 bits. Need the decision from UL physicalstructure section) Initial ranging codes 6 64 RNG codes (Need thedecision from UL Ctrl section) Initial ranging backoff start 4 Initialbackoff window size for initial ranging contention. expressed as a powerof 2. Values of n range 0-15 (Need the decision from UL Ctrl or MACoperation section) Bandwidth request backoff start 4 Initial backoffwindow size for conten- tion BRs. expressed as a power of 2. Val- ues ofn range 0-15 (the highest order bits shall be unused and set to 0) (Needthe decision from UL Ctrl or MAC operation section) Bandwidth requestbackoff end 4 Final backoff window size for contention BRs. expressed asa power of 2. Values of n range 0-15 (Need the decision from UL Ctrl orMAC operation section) NSP ID 24  Network service provider ID Additionalbroadcast information TBD indicator (ABI) MS Transmit Power LimitationLevel 8 Unsigned 8-bit integer. Specifies the maximum allowed MStransmit power. Values indicate power levels in 1 dB steps starting from0 dBm Minimum level of power offset TBD adjustment Maximum level ofpower offset TBD adjustment reserved }

The uplink Frequency Partition Configuration (UFPC) information isexpressed as above table 4. Also, the BS may signal (or broadcast) anuplink IoT control parameter of each frequency partition to the MS. Thefollowing Table 5 illustrates an example of the format of signaling ofthe uplink IoT control parameter for each frequency partition.

TABLE 5 Syntax Size (bits) Notes IE format ( ) { Default UL IoT control4 bits The UL IoT control parameter is γ_(IoT). parameter When Uplinkfrequency Partition Count (UFPCT) = 1, this value may be applied to FP0.When UFPCT = 3, this value may be applied to a specific partition foreach cell among frequency partitions of frequency reuse factor 3. WhenUFPCT = 4, this value is applied to FP0 and one of frequency partitionsof FRF 3. Relative adjustment of IoT 2 or 3 bits This value is appliedto frequency control parameter partitions other than a frequencypartition that uses the default value alone. For example, when Uplinkfrequency Partition Count (UFPCT) = 4 and the designated frequencypartition of FRF 3 is FP1, γ_(IoT) for FP2 and FP3 is a default γ_(IoT)applied to FP0 and FP1 minus a relative adjustment. Instead of therelative adjustment, an absolute value for frequency partitions otherthan a frequency partition that uses the default value alone may besignaled. }

Referring to Table 5, the BS may signal a default γ_(IoT) value for eachfrequency partition and may additionally signal a relative adjustmentvalue to the default γ_(IoT) for a specific frequency partition.

First, a method for signaling a default uplink IoT control parameterwill be described. Here, the uplink IoT control parameter may berepresented by γ_(IoT).

The default γ_(IoT) may be equal or different for each frequencypartition. For example, one 4-bit default γ_(IoT) may be commonlyapplied to all partitions and 4 bits may also be individually allocatedto each partition.

In addition, the BS may signal a relative adjustment value of the IoTcontrol parameter for each frequency partition. This value is applied tofrequency partitions other than a frequency partition which uses thedefault value alone. A specific partition among three partitions offrequency reuse factor 3 may be a partition which uses the defaultγ_(IoT) alone. Here, the specific partition may be different for eachcell (or sector). The specific partition may be determined in acell-specific manner. For example, when the specific partition, whichuses the default γ_(IoT) alone, among three partitions of frequencyreuse factor 3 is FP1 in cell 1, the specific partition may be FP2 incell 2 and the specific partition may be FP3 in cell 3.

The partition that has been determined in a cell-specific manner amongthe three partitions of frequency reuse factor 3 may be signaled to theMS through an SFH, ABI, A-MAP, or message type or may be determined in atype such as a partition number (=mod (cell ID, 3)) that is determinedin a cell-specific manner.

In the case where the number of frequency partitions is 4 in cell 1 andthe specific partition among 3 frequency partitions of frequency reusefactor 3 is FP1, only the default γ_(IoT) may be directly applied to FP0and FP1 and a value obtained by subtracting the relative adjustmentvalue from the default γ_(IoT) may be applied to FP2 and FP3.Accordingly, as a simple signaling method, the BS may additionallysignal the relative adjustment value for FP2 and FP3.

Alternatively, BS may signal an absolute value instead of the relativeadjustment value for frequency partitions other than a frequencypartition which uses the default value alone. For example, if the numberof frequency partitions is 4, a default γ_(IoT) value may be transmittedfor a specific partition (for example, FP1) among partitions offrequency reuse factor 3 and the partition FP0 of frequency reuse factor1 and a default γ_(IoT) value may be transmitted for the remainingpartitions FP2 and FP3 of frequency reuse factor 3. That is, a 4-bitdefault γ_(IoT) value may be signaled for FP0 and FP1 and a 4-bitdefault γ_(IoT) value may be signaled for FP2 and FP3.

Unlike the above signaling method in which a 4-bit γ_(IoT) value issignaled for frequency partitions using the default value, a 2 or 3-bitmay be additionally signaled in the case of the signaling method whichuses the relative adjustment value.

As the above description, the uplink IoT control parameter forcontrolling the inter-cell interference level is expressed as γ_(IoT),it may also be expressed as another symbol such as Δ_(IoT) or γ etc.

The following is a description of power control equations for open-looppower control. A transmission power level for each stream for uplinkphysical channel transmission can be represented by a variety ofoptional equations as follows.

[Mathematical Expression 35]

P _(Tx)=min(P _(Tx,1), Target IoT−PL _(i)−10 log 10(MT_(T)))[dBm]  (Option 1)

where, P _(Tx,1) =PL _(s)+NI+SINR_(Target)+Offset_(perAMS)+Offset_(perABS)[dBm].

[Mathematical Expression 36]

P _(Tx)=min(P _(Tx,1), Target IoT−PL _(i))−10 log 10(MT _(T))[dBm]  (Option 2)

where, P _(Tx,1) =PL _(s)+NI+SINR_(Target)+Offset_(perAMS)+Offset_(perABS)[dBm].

$\begin{matrix}{\mspace{20mu} \left\lbrack {{Mathematical}\mspace{14mu} {Expression}\mspace{14mu} 37} \right\rbrack} \\{P_{Tx\_ Temp} = {{PL}_{s} + {NI} + {SINR}_{Target} + {Offset}_{perAMS} + {{Offset}_{perABS}\mspace{14mu}\lbrack{dBm}\rbrack}}} \\{\mspace{20mu} {{P_{{Inter}\text{-}{cell}} = {{PL}_{i} + {{target}\mspace{14mu} {IoT}} + {Offset}_{perAMS} + {{Offset}_{perABS}\mspace{14mu}\lbrack{dBm}\rbrack}}},}} \\\begin{matrix}{P_{Tx} = \left\{ \begin{matrix}{{P_{Tx\_ Temp} - {10\log \; 10\left( {MT}_{T} \right)}},{{if}\mspace{14mu} \left( {P_{Tx\_ Temp} \leq P_{{Inter}\text{-}{cell}}} \right)}} \\{{P_{{Inter}\text{-}{cell}} - {10\log \; 10\left( {MT}_{T} \right)}},{{if}\mspace{14mu} \left( {P_{Tx\_ Temp} > P_{{Inter}\text{-}{cell}}} \right)}}\end{matrix} \right.} & {\mspace{45mu} \left( {{Option}\mspace{14mu} 3} \right)}\end{matrix}\end{matrix}$

[Mathematical Expression 38]

P _(Tx)=α·PL+NI+SINR_(Target)+Offset_(perAMS)+δ_(PowerScaling)+ICI_(offset)[dBm]  (Option4)

P _(tx) _(—) _(temp)=α·PL+NI+SINR_(Target)+Offset_(perAMS)+δ_(PowerScaling).

ICI_(Offset)={0 if P _(tx) _(—) _(temp) <P _(Inset-cell) , P_(Inset-cell) −P _(tx) _(—) _(temp) if else}

P _(Inter-cell)=Target IoT−PL _(i)[dBm]

[Mathematical Expression 39]

P _(Tx)=min(PL+NISINR_(Target)+Offset_(perAMS)+δ_(PowerScaling) , P_(Inter-cell))[dBm]  (Option 5)

where,

P _(Inter-cell)=Target IoT−PL _(i)[dBm],

[Mathematical Expression 40]

P _(Tx)=min(PL+NI+SINR_(Target)+Offset_(perAMS)+Offset_(perABS)+10 log10(1/MT _(T)), P _(Inter-cell))[dBm]  (Option 6)

where, P _(inter-cell)=Target IoT−PL _(i)[dam]

[Mathematical Expression 41]

PTx=min(PL+NI+SINR_(Target)+Offset_(perAMS)+Offset_(perABS)+10 log 10(MT_(T))), P _(target IoT))[dBm].   (Option 7)

where, P _(target IoT)=Target IoT−PL _(i)[dBm].

$\begin{matrix}{\mspace{20mu} \left\lbrack {{Mathematical}\mspace{14mu} {Expression}\mspace{14mu} 42} \right\rbrack} \\{P_{Tx\_ Temp} = {{PL}_{s} + {NI} + {SINR}_{Target} + {Offset}_{perAMS} + {{Offset}_{perABS}\mspace{14mu}\lbrack{dBm}\rbrack}}} \\\begin{matrix}{\mspace{20mu} {{P_{{target}\mspace{14mu} {IoT}} = {{{Target}\mspace{14mu} {IoT}} - {{PL}_{i}\mspace{14mu}\lbrack{dBm}\rbrack}}},}} & {\mspace{194mu} \left( {{Option}\mspace{14mu} 8} \right)}\end{matrix} \\{\mspace{20mu} {P_{Tx} = \left\{ \begin{matrix}{{P_{Tx\_ Temp} - {10\log \; 10\left( {MT}_{T} \right)}},{{if}\mspace{14mu} \left( {P_{Tx\_ Temp} \leq P_{Target\_ IoT}} \right)}} \\{{P_{Target\_ IoT} - {10\log \; 10\left( {MT}_{T} \right)}},{{if}\mspace{14mu} \left( {P_{Tx\_ Temp} \leq P_{Target\_ IoT}} \right)}}\end{matrix} \right.}}\end{matrix}$

In the above Mathematical Expressions 35 to 42, P_(TX) denotes atransmission power level for each stream at a MS for obtaining aspecific SINR_(Target), PL_(s) denotes pathloss for a serving cellestimated by the MS, PL_(i) denotes pathloss for a cell with thestrongest interference estimated by the MS, and NI denotes an averagepower level (dBm) of noise and interference of each subcarrier estimatedby the serving cell. The NI level of each frequency partition may bebroadcasted through control signaling such as an S-SFH or ABI.SINR_(Target) denotes a target SINR for data and control channeltransmission and Offset_(perAMS) denotes a correction term for aspecific-MS power offset. The BS may control Offset_(perAMS) using apower control message through an A-MAP in the case where mode switchingis performed between open-loop power control and closed-loop powercontrol. Offset_(perABS) denotes a transmission power level adjustmentvalue that is controlled by the MS. MT_(T) denotes the number of streamsindicated by a UL A-MAP IE. In the case of single-user MIMO, this valueis set to M_(t) which is the number of streams per user. In the casewhere CSM, this value is set to M_(t) _(—) A which is the total numberof streams. This value may be set to “1” in the case of control channeltransmission. TargetIoT may be broadcast to other sectors through anS-SFH. Here, the target IoT level may be different for each frequencypartition.

In Options 1 to 7 of the above Mathematical Expressions 35 to 42, avalue may be taken into consideration when compensating for a pathlosscomponent for a serving cell or a non-serving cell as in Option 3. Whenthe α value is applied to the equations of Option 3, it may be used in acell-common manner or in a user-specific manner. In a system whichemploys frequency partitions, a different α value may be applied to eachfrequency partition. P_(inter-cell) and P_(targetIoT) have the samemeaning in the above equations. δ_(PowerScaling) has the same meaning as(10 log 10(MT_(T))) and thus has the same value as (10 log 10(MT_(T))).

The BS may signal an NI level to the MS through an S-SFH. Here, theinformation that the BS signals to the MS may include an average NIlevel [dBm] of subcarriers used when frequency partitions are not takeninto consideration and an additional NI level of a sounding channel(NI_level_sounding_ch) [dBm]. On the other hand, in the case of a methodin which frequency partitions are applied among the NI level signalingmethods, an NI level for each frequency partition and an NI level ofeach sounding channel (NI_level_sounding_ch) [dBm] may be signaled.

FIG. 10 illustrates an example wherein a sounding channel configurationis transmitted in one OFDM symbol in certain frame period.

Referring to FIG. 10, a time/frequency region for transmission ofsounding information in one symbol needs to be discriminated, in termsof channel characteristics, from a time/frequency region fortransmission of other data. Although FIG. 10 illustrates that the lastsymbol is used as a sounding channel, location of symbol used as thesounding channel is not limited to last symbol. In addition, more thanone symbol may be used as the sounding channel.

The legacy power control mechanism has been based on single usertransmission of each allocated resource unit. In order to extend theuplink power control operation so as to support multiple users, there isa need to control transmission power such that the interference levelwhen multi-user transmission is used is maintained at the level ofsingle user transmission. The following Table 6 illustrates comparisonof SIMO, CSM with consideration of the number of streams, and CSMwithout consideration thereof in terms of system throughput, celledge-user throughput, and IoT level.

TABLE 6 CSM without consideration CSM with consideration SIMO of thenumber of streams of the number of streams System throughput 2.5752 Mbps2.24 Mbps 2.9231 Mbps (0.70 bps/Hz) (0.602 bps/Hz) (0.79 bps/Hz) 5%-tileuser throughput 57.79 kbps 51.71 kbps 64.43 kbps (spectral efficiency)(0.0156 bps/Hz) (0.0140 bps/Hz) (0.0174 bps/Hz) IoT Mean 5.959 6.34175.9195 level Std. 0.6836 0.7505 0.5401

In the power control method suggested in the above

Mathematical Expression 35, power adjustment is performed taking intoconsideration a target IoT such that transmission power does not exceeda power level at which the target IoT to other cells is achieved.

The following Table 7 illustrates uplink system-level simulationassumptions for the results illustrated in the above Table 6.

TABLE 7 Topic Baseline System Assumptions Basic modulation QPSK, 16QAMDuplexing scheme TDD Subchannelization PUSC Resource Allocation PUSC: 1slot (1 slot = 1 subchannel x 3 OFDMA symbols) Granularity Downlinkpilot structure Specific to Subchannelization scheme PUSC Multi-antennaTransmission SIMO (1x2) format CSM Receiver Structure MRC for SIMO, MMSEfor CSM Data Channel coding Convolutional Turbo Coding (CTC) ControlChannel Coding CDMA Codes (PUSC 2 symbols) for Initial Ranging andHandover, CDMA Codes (PUSC 1 symbol) for Periodic Ranging and BandwidthRequest, CQICH (6 bits) Scheduling Proportional Fairness for full bufferdata only Link adaptation QPSK(1/2) with repetition 1/2/4/6, QPSK(3/4),16QAM(1/2), 16QAM(3/4) Link to System Mapping MMIB H-ARQ Chase CombiningSynchronous, Nonadaptive, 1 frame ACK/NACK delay, Maximum 4 HARQRetransmissions, initial target PER of 20% Power Control Simulationscenario specific Interference Model Frequency selective interferencemodel for PUSC/AMC, no interference awareness at receiver FrequencyReuse 3 Sectors with Frequency Reuse Factor of 1 Control SignalingInitial Ranging, Periodic Ranging, Handover Ranging, Bandwidth Request,Fast Feedback/CQI Channel, Sounding

The following Table 8 illustrates comparison of power control schemeswith and without consideration of target IoT.

TABLE 8 Without power With power adjustment in adjustment considerationof target IoT Average user throughput 311.40 kbps 324.85 kbps (4.3%↑)(spectral efficiency) (0.830 bps/Hz) (0.866 bps/Hz) 5%-tile userthroughput 46.84 kbps 73.58 kbps (57%↑) (spectral efficiency) (0.012bps/Hz) (0.020 bps/Hz)

It can be seen from Table 8 that both the average user throughput andthe cell-edge user throughput are improved when power adjustment isperformed in consideration of the target IoT.

The following Table 9 illustrates a test scenario for the resultsillustrated in the above Table 8.

TABLE 9 Baseline Configuration Scenario/Parameters (Calibration & SRD)Urban Macrocell Requirements Mandatory Mandatory Site-to-Site distance1.5 km 0.5 km 1.5 km Carrier Frequency 2.5 GHz 2.5 GHz OperatingBandwidth 10 MHz for TDD 10 MHz for TDD BS Height 32 m 32 m MS Tx Power23 dBm 23 dBm MS Height 1.5 m 1.5 m Penetration Loss 10 dB 10 dBPathloss Model Loss (dB) = 130.62 + Loss (dB) = 35.2 + 35log₁₀(R) +37.6log₁₀(R) 26log₁₀(f/[GHz]/2) (R in km) (R in m) Lognormal Shadowing 8dB 8 dB Standard Deviation Correlation distance for 50 m TBD [50 m]shadowing Mobility 0-120 km/hr 0-120 kmph Channel Mix ITU Ped B * 3km/hr - Mix or specific 60% ITU Veh A 30 km/hr - 30% ITU Veh A 120km/hr - 10% Spatial Channel Model ITU with spatial correlation a)Uncorrelated b) Correlated (BS Correlation Coefficient = 0.5)

The following Table 10 illustrates simulation assumptions for theresults illustrated in the above Table 8.

TABLE 10 Parameters Baseline Configuration Site-to-Site Distance 1.5 kmCarrier Frequency 2.5 GHz Operating Bandwidth 10 MHz for TDD BS Height32 m MS Tx Power 23 dBm MS Height 1.5 m Penetration Loss 10 dB Pathlossmodel Loss(dB) = 130.62 + 37.6log₁₀(R) (R in km) Lognormal Shadowing 8dB Standard Deviation Correlation Distance for 50 m Shadowing ChannelType ITU Ped B Mobility 3 km/hr Spatial Channel Model ITU with spatialcorrelation Basic Modulation QPSK, 16QAM Duplexing Scheme TDDSubchannelization CRU Allocation Multi-antenna Transmission 1x2 SIMOFormat Receiver Structure MMSE Data Channel Coding Convolutional TurboCoding (CTC) Scheduling Proportional Fairness (PF) for full buffer dataonly 10 active users/sector Fixed control overhead of 3 symbols, 15symbols for data, 4 partitions of 48 sub-channels Link Adaptation 7levels, QPSK(1/2) with repetition 1/2/3/4, QPSK(3/4), 16QAM(1/2),16QAM(3/4) Link to System Mapping MMIB HARQ Adaptive HARQ, Up to 4retransmissions, retransmission at intervals of 3 frames InterferenceModel Average interference in used band Frequency Reuse Factor(FRF) 3sectors with FRF = 1, FRF 1/3 for FFR operation Users dropped Uniformlyin entire cell

The following Mathematical Expression 43 may be used as an equation foruplink open-loop power control.

P(dBm)=L+SINR_(Target) +NI+OffsetAMS_(perAMS)+OffsetABS_(perAMS)  [Mathematical Expression 43]

Here, SINR_(Target) is the target uplink SINR received from the BS. Amode used to calculate this value is signaled through a power controlmessage. P is the transmission power level (dBm) per stream and persubcarrier for the current transmission. L is an estimated averagecurrent UL propagation loss. This value includes a transmission antennagain and pathloss of the MS. NI is an estimated average power level(dBm) of noise and interference per subcarrier at the BS and does notinclude the BS's receive antenna gain. OffsetAMS_(perAMS) is acorrection term for an MS-specific power offset. This value iscontrolled by the MS and its initial value is zero. OffsetABS_(perAMS)is a correction term for an MS-specific power offset. This value iscontrolled by the BS through a power control message.

The estimated average current UL propagation loss L is calculated basedon the total power received in active subcarriers of the frame preamble.When the user connects to a network, it is possible to performnegotiation on the parameters using the following MathematicalExpression 44.

$\begin{matrix}{\mspace{484mu} \left\lbrack {{Mathematical}\mspace{14mu} {Expression}\mspace{14mu} 44} \right\rbrack} \\{{SINR}_{Target} = \left\{ \begin{matrix}\begin{matrix}{{{10\log \; 10\left( {\max \begin{pmatrix}{{10^{\bigwedge}\left( \frac{{SINR}_{MIN}({dB})}{10} \right)},} \\{{\gamma_{IoT} \times {SINR}_{DL}} - \alpha}\end{pmatrix}} \right)} -},} \\{\beta \times 10\log \; 10({TNS})}\end{matrix} & {{OLPC}\mspace{14mu} {Mode}\mspace{14mu} 1} \\{{{C/N} - {10\log \; 10(R)}},} & {{OLPC}\mspace{14mu} {Mode}\mspace{14mu} 2}\end{matrix} \right.}\end{matrix}$

where, C/N is a normalized C/N of the modulation/FEC rate of the currenttransmission. R is the number of repetitions for the modulation/FECrate. The OLPC mode 1 is a target SINR value for IoT control andtradeoff between the overall system throughput and the cell edgeperformance and is determined by the control parameter γ_(IoT) andSINR_(MIN). Each parameter used in the OLPC mode 1 is described asfollows.

SINR_(MIN) is the minimum SINR rate required by a BS and is set by aunicast power control message. SINR_(MIN) is represented in 4 bits. Thisvalue may be, for example, one of {−∞, −3, −2.5, −2, −1.5, −1, 0, 0.5,1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5}. γ_(IoT) is a fairness and IoT controlfactor, which is broadcast by the BS. γ_(IoT) has 4 bits, the value ofwhich may be, for example, one of {0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7,0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5}. The γ_(IoT) value may bedifferent for each frequency partition.

SINR_(DL) is the ratio of downlink signal power to noise plusinterference power, which may be measured by the MS. α is a factoraccording to the number of receive antennas at the BS. This value issignaled through 3-bit MAC power control mode signaling and can berepresented by one of {1, ½, ¼, ⅛, 1/16, 0}. β may be set to be zero orone through 1-bit MAC power control mode signaling. TNS is the totalnumber of streams in a Logical Resource Unit (LRU) indicated by a ULA-MAP IE. In case of SU-MIMO, this value is set to M_(t) which is thenumber of streams per user. In case of CSM, this value is set to TNSwhich is the total number of streams. In case of control channeltransmission, this value may be set to 1.

Uplink power control includes not only open-loop power control describedabove but also closed-loop power control. In closed-loop power control,MS transmission power is adjusted through a power control A-MAP from theBS to compensate for channel changes. In order to maintain a specificpower density at the BS at a modulation/FEC rate used by each MS, the BSmay change not only the modulation and FEC rate allocated to the MS butalso transmission power of the MS using a power control A-MAP.

Power control algorithm parameters may be optimized on a system-widebasis by the BS, may be broadcast periodically, and may be signaled byevent triggering. The MS may transmit necessary information such aspower headroom through a MAC message to the BS to support uplink powercontrol. The BS may exchange necessary information with neighbor BSsthrough the backbone network to support uplink power control. Uplinkpower control for calculating the power of each stream is performedtaking into consideration the number of streams multiplexed in the sameallocated resource.

The transmission power level per stream for uplink physical channels ofclosed-loop power control may be represented by the following options.

$\begin{matrix}{\mspace{20mu} \left\lbrack {{Mathematical}\mspace{14mu} {Expression}\mspace{14mu} 45} \right\rbrack} \\\begin{matrix}{\left. {P_{Tx} = {P_{last} + \Delta_{SINR} + \Delta_{PowerAdjust} - {10\log \; 10\left( {MT}_{T} \right)}}} \right)\mspace{14mu}\lbrack{dBm}\rbrack} & {\mspace{65mu} \left( {{Option}\mspace{14mu} 1} \right)}\end{matrix} \\{\mspace{20mu} \left\lbrack {{Mathematical}\mspace{14mu} {Expression}\mspace{14mu} 46} \right\rbrack} \\\begin{matrix}{\mspace{20mu} {{P_{Tx\_ Temp} = {P_{last} + \Delta_{SINR} + {\Delta_{PowerAdjust}\mspace{14mu}\lbrack{dBm}\rbrack}}},}} & {\mspace{115mu} \left( {{Option}\mspace{14mu} 2} \right)}\end{matrix} \\{\mspace{20mu} {P_{Tx} = \left\{ \begin{matrix}{{P_{Tx\_ Temp} - {10\log \; 10\left( {MT}_{T} \right)}},{{if}\mspace{14mu} \left( {P_{Tx\_ Temp} \leq P_{{Inter}\text{-}{cell}}} \right)}} \\{{P_{{Inter}\text{-}{cell}} - {10\log \; 10\left( {MT}_{T} \right)}},{{if}\mspace{14mu} \left( {P_{Tx\_ Temp} > P_{{Inter}\text{-}{cell}}} \right)}}\end{matrix} \right.}}\end{matrix}$

In Mathematical Expressions 45 and 46, P_(Tx) denotes a transmissionpower level per stream of an MS, P_(last) denotes the latest transmittedmaximum power level among different uplink physical channels transmittedat the same time, Δ_(SINR) denotes the difference between the desiredSINRs of previous and new MCS levels for an uplink physical channel.Δ_(PowerAdjust) denotes a power difference transmitted by thecorresponding BS through a power control A-MAP. MT_(T) has the samemeaning as that of the above Mathematical Expressions 35 to 42.

FIG. 11 is a block diagram illustrating a configuration of a preferredembodiment of an MS that can transmit signals according to the presentinvention.

Referring to FIG. 11, the MS may include a reception module 1110, aprocessor 1120, a memory unit 1130, and a transmission module 1140.

The reception module 1110 can receive all downlink signals transmittedfrom a BS. For example, the reception module 1110 can receive aparameter (for example, an IoT control parameter) for controllinginter-cell interference of each frequency partition, information of aminimum signal to interference plus noise ratio (SINR) required by theBS, information of a Noise and Interference (NI) level measured by theBS, etc.

The processor 1120 may include a transmission power control module 1121.The transmission power control module 1121 can control a transmissionpower level for transmission from the MS using information of the levelof interference between neighbor cells received through the receptionmodule 1110. Here, each MS can determine a transmission power level fora frequency partition allocated to the MS. The MS can control atransmission power level using an inter-cell interference level controlparameter received from the BS. In this case, transmission power levelcontrol may be performed periodically.

The memory unit 1130 can store information such as the inter-cellinterference level information received from the BS and the transmissionpower level determined by the transmission power control module 1121 fora specific time and the memory unit 1130 can be replaced with anothercomponent such as a buffer (not shown).

The transmission module 1140 can transmit signals to the BS at thedetermined transmission power level.

The above embodiments are provided by combining components and featuresof the present invention in specific forms. The components or featuresof the present invention should be considered optional unless explicitlystated otherwise. The components or features may be implemented withoutbeing combined with other components or features. The embodiments of thepresent invention may also be provided by combining some of thecomponents and/or features. The order of the operations described abovein the embodiments of the present invention may be changed. Somecomponents or features of one embodiment may be included in anotherembodiment or may be replaced with corresponding components or featuresof another embodiment. It will be apparent that claims which are notexplicitly dependent on each other can be combined to provide anembodiment or new claims can be added through amendment after thisapplication is filed.

The embodiments of the present invention can be implemented by hardware,firmware, software, or any combination thereof. In the case where thepresent invention is implemented by hardware, an embodiment of thepresent invention may be implemented by one or more application specificintegrated circuits (ASICs), digital signal processors (DSPs), digitalsignal processing devices (DSPDs), programmable logic devices (PLDs),field programmable gate arrays (FPGAs), processors, controllers,microcontrollers, microprocessors, or the like.

In the case where the present invention is implemented by firmware orsoftware, the embodiments of the present invention may be implemented inthe form of modules, processes, functions, or the like which perform thefeatures or operations described above. Software code can be stored in amemory unit so as to be executed by a processor. The memory unit may belocated inside or outside the processor and can communicate data withthe processor through a variety of known means.

Those skilled in the art will appreciate that the present invention maybe embodied in other specific forms than those set forth herein withoutdeparting from the spirit and essential characteristics of the presentinvention. The above description is therefore to be construed in allaspects as illustrative and not restrictive. The scope of the inventionshould be determined by reasonable interpretation of the appended claimsand all changes coming within the equivalency range of the invention areintended to be embraced in the scope of the invention.

INDUSTRIAL APPLICABILITY

The signal transmission method for a wireless communication systemaccording to the present invention can be used for industrial purposes.

1-20. (canceled)
 21. A method for transmitting signal, at a mobilestation, in a wireless communication system, the method comprising:receiving information of a specific frequency partition allocated to themobile station according to a fractional frequency reuse scheme;receiving parameter information for controlling an inter-cellinterference level for each frequency partition from a base station;determining a transmission power level for the allocated specificfrequency partition using the received information; and transmitting asignal to the base station at the determined transmission power level.22. The method according to claim 21, wherein the inter-cellinterference control parameter includes default inter-cell interferencecontrol parameter information representing a default value of eachfrequency partition and relative adjustment inter-cell interferencecontrol parameter information representing a relative difference valuefrom the default inter-cell interference control parameter value for aspecific frequency partition.
 23. The method according to claim 22,wherein a frequency partition which uses the default inter-cellinterference control parameter alone is determined according to a numberof predefined frequency partitions.
 24. The method according to claim23, wherein if the number of predefined frequency partitions is 1, thefrequency partition which uses the default inter-cell interferencecontrol parameter alone corresponds to a frequency partition of afrequency reuse factor of
 1. 25. The method according to claim 23,wherein if the number of predefined frequency partitions is 3, thefrequency partition which uses the default inter-cell interferencecontrol parameter alone corresponds to a specific frequency partitionamong frequency partitions of a frequency reuse factor of
 3. 26. Themethod according to claim 25, wherein a specific frequency partitionamong frequency partitions of the frequency reuse factor of 3 isdifferent for each cell.
 27. The method according to claim 23, whereinif the number of predefined frequency partitions is 4, the frequencypartition which uses the default inter-cell interference controlparameter alone corresponds to a specific frequency partition amongfrequency partitions of a frequency reuse factor of 3 and a frequencyreuse factor of
 1. 28. The method according to claim 27, wherein thedefault inter-cell interference control parameter value is signaled in 4bits from the base station.
 29. The method according to claim 26,wherein a specific frequency partition among the frequency partitions ofa frequency reuse factor of 3 is different for each cell.
 30. The methodaccording to claim 25, wherein the specific frequency partition amongthe frequency partitions of a frequency reuse factor of 3 is notifiedthrough broadcast signaling, or individual signaling for each mobilestation.
 31. The method according to claim 20, wherein the specificfrequency partition among the frequency partitions of a frequency reusefactor of 3 is determined as a cell Identifier (ID) function.
 32. Themethod according to claim 22, wherein the relative adjustment inter-cellinterference control parameter value is used for a specific frequencypartition among frequency partitions of a frequency reuse factor of 3.33. The method according to claim 32, wherein the relative adjustmentinter-cell interference control parameter value is signaled in 2 or 3bits from the base station.
 34. The method according to claim 21,wherein the determining of the transmission power level includesdetermining transmission power additionally taking into consideration adownlink signal to interference plus noise ratio (SINR) measured at themobile station.
 35. The method according to claim 34, further comprisingreceiving, from the base station, at least one of a minimum requiredSignal to Interference plus Noise Ratio (SINR), a factor value accordingto a number of receive antennas of the base station, and a valueindicating a MAC power control mode.
 36. The method according to claim35, wherein the transmission power level is determined by the followingMathematical Expression A: [Mathematical Expression A]${SINR}_{Target} = {{10\log \; 10\left( {\max \left( {{10^{\bigwedge}\left( \frac{{SINR}_{MIN}({dB})}{10} \right)},{{\gamma_{IoT} \times {SINR}_{DL}} - \alpha}} \right)} \right)} - {\beta \times 10\log \; 10({TNS})}}$where SINR_(MIN) is the minimum SINR required by the base station,γ_(IoT) is an inter-cell interference control parameter, SINR_(DL) is adownlink signal to noise plus interference power ratio, α is a factoraccording to the number of receive antennas at the base station, β is aMAC power control mode signaling factor, and TNS is a total number ofstreams in a Logical Resource Unit (LRU) indicated by a UL A-MAP IE. 37.The method according to claim 23, wherein the default inter-cellinterference control parameter value is equal for all frequencypartitions or for a specific frequency partition group among the allfrequency partitions or is different for each frequency partition. 38.The method according to claim 21, wherein the inter-cell interferencecontrol parameter is determined through coordination between the basestations.
 39. The method according to claim 22, wherein the inter-cellinterference control parameter is signaled to the mobile station througha control channel or message.
 40. The method according to claim 39,wherein the control channel is one of a superframe header, an uplinkAdvanced-MAP Information Element (A-MAP IE), and Additional BroadcastInformation (ABI).